Access parent context when using this.props.children in React - reactjs

Given the following, is it possible to access the parent context rather than the containers from a child (non-react component) element?
The example logs container, ideally it would log parent. I would like for Parent to be self contained, not to have it's state managed by its container.
var Container = React.createClass({
getInitialState: function () {
return {
context: 'container'
}
},
render: function () {
return (
<Parent>
<a href="#" onClick={function () {console.log(this.state.context);}.bind(this)}>click me</a>
</Parent>
);
}
});
var Parent= React.createClass({
getInitialState: function () {
return {
context: 'parent'
}
},
render: function () {
return (
<div>
{this.props.children}
</div>
);
}
});
If there is another pattern for handling this, please share as well.
Note: To be clear, I understand how the this keyword works and why the above example works as it does. The example is simply meant to illustrate the problem.

You can import some React helpers for that:
var React = require('react')
...
var children = React.Children.map(this.props.children, child => {
return React.cloneElement(child, {
context: this.state.context
})
})
render() {
return <div>{ children }</div>
}
...
Then your child component will have this.props.context which will be the string 'parent', but this must be a React component, as this needs to refer to the component using the parent prop
var YourComponent = React.createClass({
render() {
return (
<a href="#" onClick={() => console.log(this.props.context)}>
click me
</a>
)
}
})
------
var Parent = require('./Parent')
var YourComponent = require('./YourComponent')
...
render() {
return <Parent><YourComponent /></Parent>
}

I do not know about the first part of your question, but since you commented about dynamically creating components, here's how I do it:
You can set a state variable in the constructor of the class and its parent:
if (typeof this.state == 'undefined') {
this.state = {
componentsToRender: <div></div>
};
}
Then in the parent component, in the componentDidMount() function:
var componentsToRender = [];
if ([conditional]) {
// some logic so you know which component to render
componentsToRender.push(<customChildComponentToRender key={} />);
}
else {
componentsToRender.push(<otherComponentToRender key={} />);
}
this.setState({
componentsToRender: <div>{componentsToRender}</div>
});
Make sure to put a key (lines 4 and 7 of the second code block) or React will scream at you.
In response to your initial question, I would watch this video from the ReactJS Conference 2015 to get more of the heart behind a container. After hearing what the guys at Facebook say (who have radical views on containers!), you might want to rethink the design to make your container more of a data layer.

I would check out THIS article from the react website. I think it might give you some intuition on solving your problem.
As a general rule of thumb, I try and only use this.state to handle internal UI state of a specific component. Everything else is passed via props. If you're needing the full context of a component, I would either pass it as a prop or checkout something like flux or redux which will help you manage state between components.

Related

ReactJS: Parent child partial update

I'm having a bit of a trouble getting my head around how i would communicate between my parent and child components in my specific use case.
I have a child component that renders some points using an external lib.
What I'm currently doing is implementing componentDidMount/Update and use the external lib to render the points in this.props.points (which is an array provided by the parent component).
Rendering the points involves looping through them and call something like ExternalLib.addPoint(point).
What i would like to do, instead of looping through all the points everytime this.props.points changes, is making the parent component add (or remove) individual points to the child component.
Is it React friendly to call something like this.refs.myChild.addPoint(point) in the parent component?
Are there other techniques to achieve something like this?
Update
Here's some code (https://jsfiddle.net/69z2wepo/61366/):
const ExternalLib = {
addPoint: function(el, point) {
var li = document.createElement("li");
li.innerHTML = point;
el.appendChild(li);
}
}
class Child extends React.Component {
componentDidMount() {
this.renderPoints();
}
componentDidUpdate() {
this.renderPoints();
}
renderPoints() {
const el = this.refs.points;
el.innerHTML = '';
this.props.points.forEach(function(point) {
ExternalLib.addPoint(el, point);
});
}
render() {
console.log('render')
return (
<div>
<ul ref="points"></ul>
</div>
);
}
}
class Parent extends React.Component {
constructor() {
super();
this.state = {
points: []
};
}
addPoint() {
const points = this.state.points.slice();
points.push((new Date()).getTime());
this.setState({
points: points
});
}
render() {
return (
<div>
<button onClick={this.addPoint.bind(this)}>Add Point</button>
<Child points={this.state.points} />
</div>
);
}
}
ReactDOM.render(
<Parent />,
document.getElementById('container')
);
This is simplified because in this example I could generate the markup directly making use of map and leveraging React's partial DOM update - the external lib does some extra stuff that's not in this question's scope.
Thanks!
If you want to interfere with React rendering process, you can code shouldcomponentupdate.
In your children, if you make shouldcomponentupdate return false and call ExternalLib.addPoint(point), it should do the job:
shouldComponentUpdate(nextProps){
//comparePoints() is a function able to find if a new point is present in the list, comparing existing used points with new one
var newPoint = comparePoints(this.props.points, nextProps.points)
if(newPoint){
ExternalLib.addPoint(newPoint);
//forbide re-render
return false;
}
//enable other update
return true;
}

How can I use dynamic react class element in render?

I understand the question is not clear, so the description will help.
So, I have some react components like,
var LandingPage = React.createClass({
render: function() {
return <div>
This is the landing page.
</div>
}
})
and another component like
var FirstContent = React.createClass({
render: function() {
return <div>
This is first content page
</div>
}
})
Now I have a controller where I decide which one I need to render by passing a value in props, something like this -
var Contoller = React.createClass({
render: function() {
var inside = "";
if (this.props.pageName == "LandingPage") {
inside = <LandingPage />;
} else if (this.props.pageName == "FirstContent") {
inside = <FirstContent />;
}
return <div>
{inside}
</div>;
}
})
Now instead, I want to do something like, use the this.props.pageName inside the tag directly, so that I don't have to write if else for every time ad some new alternate content. Should be something like this -
var Contoller = React.createClass({
render: function() {
return <div>
<"this.props.pageName" /> //comment - <LandingPage /> if this.props.pageName = "LandingPage"
</div>;
}
})
The map of pageName to actual Component has to exist somewhere, because other than the default HTML elements (like div) React needs the class object reference to render a component. A string wont do.
How you manage this map is up to you, but I've used an object below.
Further complicating this is the JSX compilation step, which doesn't work with dynamic content. You will have to use the actual JS calls in your Controller to get this working.
Here is a codepen demonstrating this.
class LandingPage extends React.Component {
render() {
return <div> This is the landing page. </div>;
}
}
class FirstContent extends React.Component {
render() {
return <div> This is the first content page. </div>;
}
}
const map = {
LandingPage: LandingPage,
FirstContent: FirstContent
};
class Controller extends React.Component {
render() {
return React.createElement(map[this.props.pageName]);
}
}
React.render(<Controller pageName={'LandingPage'} />, document.body);
All that being said, I think you are building a router. You can use react-router in memory mode to perform routing without using the URL. Rolling your own setup here may be more work than it's worth.
The map does exist in the example by Tyrsius: you can use window[this.props.pageName]. Though it's better not to expose your components to the window object. And it may not work at all if you're using CommonJS for your React components.
If you don't need to build a name of several parts, why don't you just pass the component itself instead of a string? Either as a property or, better, as a child:
class Controller extends React.Component {
render() {
return <div>{this.props.children}</div>;
}
}
React.render(<Controller><FirstContent/></Controller>, document.body);

How do I set state of sibling components easily in React?

I have got the beginnings of a clickable list component that will serve to drive a select element. As you can see from the below, onClick of the ListItem, I'm passing the state of a child element (ListItem in this case) to the parents (SelectableList, and CustomSelect component). This is working fine. However, what I would also like to do is change the state of the sibling components (the other ListItems) so that I can toggle their selected states when one of the ListItems is clicked.
At the moment, I'm simply using document.querySelectorAll('ul.cs-select li) to grab the elements and change the class to selected when it doesn't match the index of the clicked ListItem. This works - to an extent. However, after a few clicks, the state of the component has not been updated by React (only by client side JS), and things start to break down. What I would like to do is change the this.state.isSelected of the sibling list items, and use this state to refresh the SelectableList component. Could anyone offer a better alternative to what I've written below?
var React = require('react');
var SelectBox = require('./select-box');
var ListItem = React.createClass({
getInitialState: function() {
return {
isSelected: false
};
},
toggleSelected: function () {
if (this.state.isSelected == true) {
this.setState({
isSelected: false
})
} else {
this.setState({
isSelected: true
})
}
},
handleClick: function(listItem) {
this.toggleSelected();
this.props.onListItemChange(listItem.props.value);
var unboundForEach = Array.prototype.forEach,
forEach = Function.prototype.call.bind(unboundForEach);
forEach(document.querySelectorAll('ul.cs-select li'), function (el) {
// below is trying to
// make sure that when a user clicks on a list
// item in the SelectableList, then all the *other*
// list items get class="selected" removed.
// this works for the first time that you move through the
// list clicking the other items, but then, on the second
// pass through, starts to fail, requiring *two clicks* before the
// list item is selected again.
// maybe there's a better more "reactive" method of doing this?
if (el.dataset.index != listItem.props.index && el.classList.contains('selected') ) {
el.classList.remove('selected');
}
});
},
render: function() {
return (
<li ref={"listSel"+this.props.key}
data-value={this.props.value}
data-index={this.props.index}
className={this.state.isSelected == true ? 'selected' : '' }
onClick={this.handleClick.bind(null, this)}>
{this.props.content}
</li>
);
}
});
var SelectableList = React.createClass({
render: function() {
var listItems = this.props.options.map(function(opt, index) {
return <ListItem key={index} index={index}
value={opt.value} content={opt.label}
onListItemChange={this.props.onListItemChange.bind(null, index)} />;
}, this);
return <ul className="cs-select">{ listItems }</ul>;
}
})
var CustomSelect = React.createClass({
getInitialState: function () {
return {
selectedOption: ''
}
},
handleListItemChange: function(listIndex, listItem) {
this.setState({
selectedOption: listItem.props.value
})
},
render: function () {
var options = [{value:"One", label: "One"},{value:"Two", label: "Two"},{value:"Three", label: "Three"}];
return (
<div className="group">
<div className="cs-select">
<SelectableList options={options}
onListItemChange={this.handleListItemChange} />
<SelectBox className="cs-select"
initialValue={this.state.selectedOption}
fieldName="custom-select" options={options}/>
</div>
</div>
)
}
})
module.exports = CustomSelect;
The parent component should pass a callback to the children, and each child would trigger that callback when its state changes. You could actually hold all of the state in the parent, using it as a single point of truth, and pass the "selected" value down to each child as a prop.
In that case, the child could look like this:
var Child = React.createClass({
onToggle: function() {
this.props.onToggle(this.props.id, !this.props.selected);
},
render: function() {
return <button onClick={this.onToggle}>Toggle {this.props.label} - {this.props.selected ? 'Selected!' : ''}!</button>;
}
});
It has no state, it just fires an onToggle callback when clicked. The parent would look like this:
var Parent = React.createClass({
getInitialState: function() {
return {
selections: []
};
},
onChildToggle: function(id, selected) {
var selections = this.state.selections;
selections[id] = selected;
this.setState({
selections: selections
});
},
buildChildren: function(dataItem) {
return <Child
id={dataItem.id}
label={dataItem.label}
selected={this.state.selections[dataItem.id]}
onToggle={this.onChildToggle} />
},
render: function() {
return <div>{this.props.data.map(this.buildChildren)}</div>
}
});
It holds an array of selections in state and when it handles the callback from a child, it uses setState to re-render the children by passing its state down in the selected prop to each child.
You can see a working example of this here:
https://jsfiddle.net/fth25erj/
Another strategy for sibling-sibling communication is to use observer pattern.
The Observer Pattern is a software design pattern in which an object can send messages to multiple other objects.
No sibling or parent-child relationship is required to use this strategy.
Within the context of React, this would mean some components subscribe to receive particular messages and other components publish messages to those subscribers.
Components would typically subscribe in the componentDidMount method and unsubscribe in the componentWillUnmount method.
Here are 4 libraries that implement the Observer Pattern. The differences between them are subtle - EventEmitter is the most popular.
PubSubJS: "a topic-based publish/subscribe library written in JavaScript."
EventEmitter: "Evented JavaScript for the browser." It's actually an implementation of a library that already exists as part of nodejs core, but for the browser.
MicroEvent.js: "event emitter microlibrary - 20lines - for node and browser"
mobx: "Simple, scalable state management."
Taken from: 8 no-Flux strategies for React component communication which also is a great read in general.
The following code helps me to setup communication between two siblings. The setup is done in their parent during render() and componentDidMount() calls.
class App extends React.Component<IAppProps, IAppState> {
private _navigationPanel: NavigationPanel;
private _mapPanel: MapPanel;
constructor() {
super();
this.state = {};
}
// `componentDidMount()` is called by ReactJS after `render()`
componentDidMount() {
// Pass _mapPanel to _navigationPanel
// It will allow _navigationPanel to call _mapPanel directly
this._navigationPanel.setMapPanel(this._mapPanel);
}
render() {
return (
<div id="appDiv" style={divStyle}>
// `ref=` helps to get reference to a child during rendering
<NavigationPanel ref={(child) => { this._navigationPanel = child; }} />
<MapPanel ref={(child) => { this._mapPanel = child; }} />
</div>
);
}
}

Accessing methods on children

I Have a component that receives children and renders those children
component = React.createClass({
...some JSX
{this.props.children}
...some JSX
)}
At some point I need to loop around the children and call a method that they expose. However, children are not object instances, but rather React representations.
In essence I want to do something like this:
var children = this.props.children
React.Children.forEach(children, function(child) {
child.someAction()
})
What's the best way of achieving this?
There is one way that I came across on IRC and it involved cloning the children then accessing them by ref. Though it seems kind of convoluted.
// in JSX
{
newChildren = React.Children.map(children, function(child) {
return React.CloneElement(child, {ref: child.ref})
})
}
Then do
childRefs = this.props.children.map(function(child) {
return child.ref
})
var self = this;
childRefs.forEach(function(ref){
self.refs[ref].someAction()
})
Though, this feels like I'm working against React.
In generel you should always try to use to outside-in approach and think of data as immutable.
Providing all children with a shouldValidate flag as a prop and then make all children implement the componentWillReceiveProps function to do the validation, would be the preferred way as I see it.
Components should in my opinion never expose functions/properties to be called from outside as this goes against the idea of React.
An jsx example:
Parent
render: function() {
return this.children.map(Child => {
return <Child shouldValidate={this.state.submitting}/>
});
}
onSubmit: function() {
this.setState({
submitting: true
})
}
Child
componentWillReceiveProps: (nextProps) => {
if (this.props.shouldValidate) {
validate();
}
}

React context doesn't transfer when using a component as prop

I'm using react-bootstrap's ModalTrigger to show a field-heavy modal (based on react-bootstrap's Modal), which means sending it a bunch of props:
<ModalTrigger modal={<MyModal field1={value1} field2={value2} (more fields...)/>}>
Click here to open
</ModalTrigger>
The parent component that creates the trigger has the fields/values passed in via props, and the parent component of that component has it passed as props as well, by the top-level component that actually holds the data. Both are basically pipes, which is a classic childContext scenario, except that it doesn't work. Here's a simplified version of what I've tried:
var MyModal = React.createClass({
contextTypes : {foo : React.PropTypes.string},
render : function() {
return (
<Modal {...this.props} title="MyTitle">
<div className="modal-body">
The context is {this.context.foo}
</div>
</Modal>
);
}
});
var Content = React.createClass({
childContextTypes : {foo: React.PropTypes.string},
getChildContext : function() {return {foo : "bar"}},
render : function() {
return (
<ModalTrigger modal={<MyModal/>}>
<span>Show modal</span>
</ModalTrigger>
)
}
});
The modal pops up with "The context is", without showing the actual context.
I believe this is happening because the prop sent to ModalTrigger is already rendered/mounted somehow, but I'm not sure why. To the best of my understanding, the owner of MyModal is the Content component, which means that the context should be ok, but this is not the case.
Some more information: I already tried passing {...this.props} and context={this.context} to MyModal with no success. Also, maybe relevant, ModalTrigger uses cloneElement to make sure the modal's onRequestHide prop points to the trigger's hide function.
So what am I missing here? :/
React.cloneElement will change the owner of the element when the ref prop is overriden, which means context will not be passed from the previous owner. However, this does not seem to be the case with ModalTrigger.
Note that the owner-based approach won't work altogether in React 0.14, since context will be passed from parent to child and not from owner to ownee anymore. ModalTrigger renders its modal node prop in another branch of the DOM (See OverlayMixin). Thus, your Modal component is not a child nor a descendant of your Content component and won't be passed child context from Content.
As for solving your problem, you can always create a component whose sole purpose is to pass context to its children.
var PassContext = React.createClass({
childContextTypes: {
foo: React.PropTypes.string
},
getChildContext: function() {
return this.props.context;
},
render: function() {
return <MyModal />;
},
});
To use it:
<ModalTrigger modal={<PassContext context={this.getChildContext()}/>}>
As Matt Smith hinted, it turns out that react-bootstrap already includes a very similar approach to forwarding context via ModalTrigger.withContext. This allows you to create a ModalTrigger component class which will forward its context to its modal node prop, no matter its position in the VDOM tree.
// MyModalTrigger.js
module.exports = ModalTrigger.withContext({
foo: React.PropTypes.String
});
There is a much better way of passing context on to your "portal" type components which render their children into a different container outside the React tree.
Using "renderSubtreeIntoContainer" rather than "render" will pass the context into the subtree as well.
It can be used like so:
import React, {PropTypes} from 'react';
import {
unstable_renderSubtreeIntoContainer as renderSubtreeIntoContainer,
unmountComponentAtNode
} from 'react-dom';
export default class extends React.Component {
static displayName = 'ReactPortal';
static propTypes = {
isRendered: PropTypes.bool,
children: PropTypes.node,
portalContainer: PropTypes.node
};
static defaultProps = {
isRendered: true
};
state = {
mountNode: null
};
componentDidMount() {
if (this.props.isRendered) {
this._renderPortal();
}
}
componentDidUpdate(prevProps) {
if (prevProps.isRendered && !this.props.isRendered ||
(prevProps.portalContainer !== this.props.portalContainer &&
prevProps.isRendered)) {
this._unrenderPortal();
}
if (this.props.isRendered) {
this._renderPortal();
}
}
componentWillUnmount() {
this._unrenderPortal();
}
_getMountNode = () => {
if (!this.state.mountNode) {
const portalContainer = this.props.portalContainer || document.body;
const mountNode = document.createElement('div');
portalContainer.appendChild(mountNode);
this.setState({
mountNode
});
return mountNode;
}
return this.state.mountNode;
};
_renderPortal = () => {
const mountNode = this._getMountNode();
renderSubtreeIntoContainer(
this,
(
<div>
{this.props.children}
</div>
),
mountNode,
);
};
_unrenderPortal = () => {
if (this.state.mountNode) {
unmountComponentAtNode(this.state.mountNode);
this.state.mountNode.parentElement.removeChild(this.state.mountNode);
this.setState({
mountNode: null
});
}
};
render() {
return null;
}
};
This is an example of a portal I use in my production app Casalova that render context properly into their children.
Note: this API is undocumented and is likely to change in the future. For now, though, it's the right way to render context into portal components.

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